Resistive temperature devices (RTD) are devices that have temperature sensing elements that vary in resistance as a function of temperature. Although the output response curves are non-linear in nature, precision temperature measurements can be readily obtained because an RTD's response will predictably follow the response curve. Measuring spatial differences in temperature using a pair of RTDs is challenging however, because simply knowing a difference in the resistances between two RTDs does not convey where either device is with respect to its response curve. As such this difference value cannot be used by itself to determine a temperature difference.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for circuits for determining differential and average temperatures from resistive temperature devices.